(a) Field of the Invention
The present invention relates to a layered transmission apparatus and method, a reception apparatus, and a reception method.
(b) Description of the Related Art
A broadcasting system, providing diverse video qualities, transmits scalable video coded image information so as to be compatible with reception apparatuses having various performances. A scalable video coding (SVC) is classifying information into a plurality of layers according to the significance of image information and transmitting the same. When a transmitter performs layered transmission to effectively transmit image information using the SVC technique, a receiver reproduces the layers according to desired image quality or device performance.
A layer modulation technique, a typical technique among layered transmission techniques, modulates video information by layer and transmits the same. Layer modulation is a scheme of transmitting a base layer and an enhancement layer, and when the layer modulation scheme uses 16QAM (Quadrature Amplitude Modulation), it can transmit two layers. Thus, in order for the transmitter to transmit more layers, a modulation order must be increased; however, in this case, the coverage is reduced and reception performance is possibly drastically degraded. In addition, the reception apparatus hitherto performs demodulation by layer, causing inter-layer interference. So, in order to solve this problem, if the transmitter assigns more transmission power to the base layer than that to the enhancement layer to reduce inter-layer interference, the distance between constellation points of the enhancement layer would become narrow, making it difficult to transmit two or more layers.